2(a).
i.
Complete the electron configuration of a bromide ion.
ii.
2s2,2p6,3s2,3p6,3d10,4s2,4p6
1s2......................................................................................................................................................
[1]
A student adds a small volume of aqueous silver nitrate to an aqueous solution of bromide ions in a test-tube. The student
then adds a similar volume of dilute aqueous ammonia to the same test-tube.
Describe what the student would see in the test-tube after the addition of aqueous ammonia.
Cream
iii.
[1]
Write an ionic equation for any precipitation reaction which occurs in the student's tests.
Include state symbols.
Ag+ (aq)
(b).
+
Br- (aq)
——>
AgBr (s)
[1]
The Group 7 element chlorine reacts with sodium hydroxide, NaOH, under different conditions to give different products.
i.
Chlorine reacts with aqueous sodium hydroxide to form bleach.
Write the equation and state the conditions for this reaction.
Cl2 (g) +
2NaOH (aq) ——> NaCl (aq)
+
NaClO (aq) +
equation ................................................................................................................................................
H2O (l)
Cold and dilute NaOH is used
conditions ................................................................................................................................................
[2]
ii.
Under different conditions, chlorine reacts differently with aqueous sodium hydroxide.
A disproportionation reaction takes place as shown below.
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3Cl2(g) + 6NaOH(aq) → 5NaCl(aq) + NaClO3(aq) + 3H2O(l)
State what is meant by disproportionation and show that disproportionation has taken place in this reaction.
Use oxidation numbers in your answer.
A Disproportionation reaction is a reaction in which a compound undergoes oxidation as well as
reduction.
The oxidation number of Cl decrease from 0 in Cl2 to -1 in NaCl, showing that Cl is being reduced
The oxidation number of Cl increase from 0 in Cl2 to +5 in NaClO, showing that Cl is being oxidesed
[3]
3.
A student bubbles chlorine gas through aqueous potassium iodide. A reaction takes place.
i.
State what the student would observe.
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Solution turns into violet colour
ii.
[1]
Write the ionic equation for this reaction.
Include state symbols.
2I- (aq)
4.
——>
I2 (aq)
+
2e-
[1]
A student carries out the following experiment to investigate the reaction between hexane and chlorine. The chlorine is made by
reaction of aqueous sodium chlorate(I) with dilute hydrochloric acid.
Procedure
1 cm3 of hexane is mixed with 1 cm3 dilute aqueous sodium
chlorate(I) in a test-tube.
Observations
1 cm3 dilute hydrochloric acid is slowly added to the mixture.
The acid mixes with the lower layer, which turns a pale green
colour.
The pale green colour moves to the upper layer, leaving the
lower layer colourless.
The tube is then stoppered and shaken.
The tube is placed under a bright light and shaken at regular
intervals for about 10 minutes. The stopper is loosened
regularly to release any pressure.
i.
The mixture forms two colourless layers.
The pale green colour slowly disappears leaving two
colourless layers after about 10 minutes.
The reaction between aqueous sodium chlorate(I) and dilute hydrochloric acid produces aqueous sodium chloride as well
as chlorine.
Suggest an equation for this reaction.
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NaClO (aq)
ii.
+
2HCl (aq)
——>
NaCl (aq)
+
Cl2 (g)
+
H2O (l)
[2]
Outline a simple practical test that would confirm the presence of chloride ions in the lower layer, and give the expected
result.
test:
result:
Add AgNO3 into a solution containing Cl- ion
...................................................................................................................................................
White precipitate will be formed
...................................................................................................................................................
[2]
iii.
Name the apparatus that could be used to separate the two liquid layers present at the end of the experiment.
Separating funnel
5.
[1]
Which halogen most readily forms 1– ions?
A.
B.
C.
D.
bromine
chlorine
fluorine
iodine
Your answer
C
[1]
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7.
Students work together in groups to identify four different solutions.
Each solution contains one of the following compounds:




ammonium sulfate, (NH4)2SO4
sodium sulfate, Na2SO4
sodium chloride, NaCl
potassium bromide, KBr.
Your group has been provided with universal indicator paper and the following test reagents:




barium chloride solution
silver nitrate solution
dilute ammonia solution
sodium hydroxide solution.
* A student in your group suggests the following plan:



Add about 1 cm depth of each solution into separate test-tubes.
Add a few drops of barium chloride solution to each test-tube.
A white precipitate will show which solutions contain sulfate ions.
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
Two of the solutions will form a white precipitate.
Describe how you would expand this plan so that all four solutions could be identified using a positive test result.
You should provide observations and conclusions that would enable your group to identify all four solutions.
Conduct halide ion test by adding few drops of AgNO3 into the two solutions that have
not formed precipitate after SO4 2- ion test
Solution containing Cl- ion will form a white precipitate, and AgCl forms
Solution containing Br- ion will form a cream precipitate, and AgBr forms
Then use dilute NH3 (aq) to confirm the precipitate by adding few drops of NH3 (aq)
into the original two precipitate(AgCl, AgBr) formed upon halide ion test
The precipitate dissolves to give a colourless solution means it was AgCl precipitate.
So NaCl is identified and the remaining halide is KBr
To test for ammonium ion on the sulphates already identified, warm the two sulphate
solution with NaOH
Apply pH test by using a moist indicator paper, the paper turns blue if ammonium gas is
present. So (NH4)2SO4 is identified and the remaining sulphate is Na2SO4
[6]
8.
Give chemical explanations for the following statements.
Bromine has a higher boiling point than chlorine.
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Because a Br2 molecules has more electron than a Cl2 molecule, so more energy is
required to break the relatively stronger induced dipole force between the Br2 molecules [1]
10.
N2O3 is an unstable oxide of nitrogen that decomposes in a redox reaction.
N2O3(g) → NO(g) + NO2(g)
i.
State the oxidation number of nitrogen in each oxide in the table below.
Oxide
N2O3
NO
NO2
Oxidation number of nitrogen
+3
+2
+4
[1]
ii.
Name this type of redox reaction.
In your answer you should use appropriate technical terms spelled correctly.
Disproportionation
11.
[1]
A student adds aqueous sodium carbonate to one test-tube and aqueous silver nitrate to a second test-tube.
The student adds dilute sulfuric acid to each test‐tube.
Which row has the correct observations?
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Aqueous sodium carbonate
no change
no change
effervescence
effervescence
A
B
C
D
Your answer
Aqueous silver nitrate
precipitate
no change
no change
precipitate
c
[1]
12(a).
Chlorine is used in water treatment.
State one benefit and one risk of chlorine in water treatment.
Provides protection against waterborne disease outbreaks
Benefit ......................................................................................................................................................
Potential long-term effects of chlorination by-products such as
Risk ..........................................................................................................................................................
Asthma
[1]
(b).
Precipitation reactions can be used to distinguish between halide ions.
i.
State the reagent needed for these precipitation reactions.
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AgNO3
ii.
[1]
How would the appearance of the precipitates allow you to distinguish between chloride, bromide and iodide ions?
White precipitate
Chloride ................................................................................................................................................
Cream precipitate
Bromide ................................................................................................................................................
Yellow precipitate
Iodide ................................................................................................................................................
[1]
13(a).
This question is about chemicals used by gardeners.
A garden product contains hydrated ammonium iron(II) sulfate, (NH4)2Fe(SO4)2•xH2O. (NH4)2Fe(SO4)2•xH2O contains 27.55% by
mass of water of crystallisation.
Calculate the value of x in the formula (NH4)2Fe(SO4)2•xH2O.
Show your working.
g
Mr
mole
mole ratio
H2O
27.55
/
18
=
1.530
6
(NH4)2Fe(SO4)2
72.45
/
284.1
=
0.255
1
(NH4)2Fe(SO4)2•6H2O
6
x = .............................
[3]
(b).
The garden product in the previous question part is a solid mixture of the following ingredients:
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


i.
Hydrated ammonium iron(II) sulfate, (NH4)2Fe(SO4)2•xH2O, which is soluble in water
Crushed limestone (calcium carbonate)
Sand.
Suggest why crushed limestone has been included in this garden product.
To neutralise soil acidity and to supply calcium (Ca) for plant nutrition
[1]
14.
Which silver compound is insoluble in concentrated NH3(aq)?
A
B
C
D
AgNO3
AgCl
AgBr
AgI
Your answer D
15.
[1]
A chemist carries out reactions of barium and barium nitride, Ba3N2.
Reaction 1
Barium is reacted with water.
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Reaction 2
Reaction 3
i.
Barium nitride is reacted with water, forming an alkaline solution and an alkaline gas.
Barium is reacted with an excess of oxygen at 500°C, forming barium peroxide, BaO2.
Write equations for Reaction 1 and Reaction 2.
Ignore state symbols.
Ba + 2H2O ——> Ba(OH)2 + 2H2
Reaction 1: ............................................................................................................................................
Ba3N2 + 6H2O ——> 3Ba(OH)2 + 2NH3
Reaction 2: ............................................................................................................................................
[3]
ii.
Predict the structure and bonding of Ba3N2.
Giant ionic structure, with ionic bonding
iii.
[1]
BaO2 formed in Reaction 3 contains barium and peroxide ions.
The peroxide ion has the structure [O−O]2−.
Suggest a ‘dot-and-cross’ diagram for BaO2.
Show outer shell electrons only.
[
16.
2+
Ba
] [
O
O
]
2-
[1]
Calcium is in Group 2 of the Periodic Table.
The diagram shows some reactions of calcium and its compounds.
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Reactions 1 and 2 both form calcium oxide.
i.
Write the equation for reaction 1.
2Ca (s) + O2 (g) ——> 2CaO (s)
ii.
[1]
What type of reaction is reaction 2?
Endothermic
17.
[1]
Which row is correct?
Highest pH when added to water
MgO
MgO
BaO
BaO
A
B
C
D
Your answer
Most reactive halogen
F2
I2
F2
I2
C
[1]
18.
Which statement is not correct for Group 2 metals?
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A.
B.
C.
D.
An unpaired electron is present in an s-orbital.
Chemical reactivity increases with increasing atomic number.
The first ionisation energy decreases with increasing atomic number.
Atomic radius increases with increasing atomic number.
Your answer
A
[1]
19.
The Group 2 elements react with water, forming a solution and a gas.
Which statement is correct?
A.
B.
C.
D.
The reactivity of the elements decreases down Group 2.
The pH of the solution formed increases down Group 2.
The reaction is a neutralisation.
The equation for the reaction of strontium with water is:
2Sr + 2H2O → 2SrOH + H2
Your answer
B
[1]
20.
This question looks at groups in the periodic table.
Calcium and strontium are Group 2 metals. They both react with water.
A chemist reacts 0.200 g of strontium with 250 cm3 water, leaving a colourless solution containing strontium ions. The volume
remains at 250 cm3.
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i.
Write an equation for the reaction between strontium and water.
Include state symbols.
Sr (s) + 2H2O (l) → Sr(OH)2 (aq) + H2 (g)
ii.
[1]
Calculate the concentration, in mol dm−3, of strontium ions in the resulting solution.
(0.2/87.62)/(250/1000)=0.00913 mol dm-3
0.00913
concentration of strontium ions = ..........................................mol dm−3 [2]
iii.
A student plans to carry out this experiment using 0.200 g of calcium instead of 0.200 g of strontium.
Predict the difference, if any, between the volume of gas produced by calcium and strontium.
Explain your reasoning and include a calculation in your answer.
Larger volume of gas will be produced if Ca is used
Because Ca has lower A_r which means larger mole of Ca is used for reaction
H2 produced by Sr = 0.00913x24x100=56.7 cm3
H2 produced by Ca = 0.2/40.1=0.00500 mol; 0.005/(250/1000)=0.200 mol of H2 —> 120 cm3
[3]
22(a).
Magnesium will undergo redox reactions with aqueous salts of less reactive metals.
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i.
A student reacts magnesium with aqueous copper(II) sulfate.
Mg(s) + CuSO4(aq) → Cu(s) + MgSO4(aq)
Explain, in terms of numbers of electron transferred, the redox processes taking place in this reaction.
Mg is oxidised as the oxidation number of Mg increase from 0 in Mg to +2 in MgSO4
Cu is reduced as the oxidation number of Cu decreases from 2+ in CuSO4 to 0 in Cu
[2]
ii.
The student also noticed that the magnesium started fizzing.
The student thought the fizzing was due to the magnesium reacting with water in the mixture.
Write the equation for the reaction of magnesium with water.
Include state symbols.
Mg (s) + 2H2O (l) ——> Mg(OH)2 + 2H2 (g)
(b).
[2]
Compounds of calcium have many uses.
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i.
Identify a compound of calcium that could be used to convert a soil pH from 5.8 to 7.5.
CaCO3
ii.
[1]
Calcium phosphide, Ca3P2, is an ionic compound used in rat poison.
Calcium phosphide can be prepared by reacting calcium metal with phosphorus, P4.
Write the equation for the reaction of calcium with phosphorus to form calcium phosphide.
6Ca (s) + P4 (s) ——> 2Ca3P2 (s)
Draw a ‘dot-and-cross’ diagram to show the bonding in calcium phosphide, Ca3P2.
Show outer electrons only.
[
Ca
[
3
2+
[
2
P
[
iii.
[1]
3+
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24(a).
This question is about Group 2 and Group 17 (7).
Barium chloride can be prepared from barium hydroxide in a neutralisation reaction.
Write the equation for this reaction. State symbols are not required.
Ba(OH)2 + 2HCl ——> BaCl2 + 2H2O
(b).
[1]
The reactivity of the Group 2 elements Mg–Ba increases down the group.
Explain why.
Because as element goes down Group 2:
the number of electron shells increase, thus the atomic radius increases
The outer electrons experience more shielding by inner electron shells
The attraction between the nucleus and the outer electrons decreases
The outer electrons are easier to be removed for chemical reaction
[3]
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